The conversion factors presented in Tu..c 3.33 have, therefore, been calculated for the ex- posed and for the shielded side of a ship. A comparison of the destroyer conversion factors determined for the two shots indicates that, although they are fairly constant, there can be variations as large as 20 percent of the mean. The comparison is by no means as good for the EC-2. These discrepancies (and possibly the abnormally high record for the bow station aboard the DD-593) are probably due to local turbulence caused by the ship’s superstructure (Section 3.3.2). Since a high reading was obtained at the bow station on the DD-593 on both shots and since no fault can be found with the detector, the reading is considered valid. Furthermore, this GITR record agrees with the other weather deck records after passage of the base surge. As previously suggested, eddies caused by the superstructure may temporarily retain remnants of the base surge at specific locations. A plot of the difference between the bow station and the other two stations aboard the DD-393 versus time (Figure 3.215) yields a record resembling that characteristic of the particular shot. The integrated dose under these curves is 288 r for Wahoo and 93 r for Umbrella. Similar eddy effects are postulated aboard all target ships (Sections 3.3.2 and 3.4.1). The temporary retention of surge in turbulent eddies surrounding the ship’s superstructure would have highly variable effects and cannot be conclusively demonstrated by the available data. A short retention at early time could result in a Significant additional dose; however, the case of the bow station on the DD-593 appears extreme. Possibly, these effects may be more pronounced after the base surge has slowed down to surface wind velocities and at times when the surge transit dose is not masking. Although retardation and temporary retention of the surge by the ship’s superstructure seems a reasonable explanation for the prolonged gamma records after upwind surge transit, the extension to the bow records for the DD-593 is at best difficult, and no completely satisfactory explanation has yet been advanced. Although the eddy hypothesis cannot be conclusively demonstrated, it does indicate possible errors in the assumption that the cumulative dose received aboard a ship corresponds to that which would be predicted on the basis of the ship’s position relative to the isodose contours and superstructure shielding factors. With these reservations, the dose determined from the isodese contours may be assumed to represent that received at an exposed position well away from the superstructure on a stationary ship under full washdown. This dose may then be converted to other less exposed positions on the weather decks, using the conversion factors listed in Table 3.33. This type of conversion may, of course, be extended to inner compartments us- ing the film pack data obtained by Project 2.1. It is impossible to estimate the true accuracy of this procedure; therefore, these conversion factors must be used with caution. This statement is particularly true if this information is further extended to the case of moving ships. 3.5 CHARACTERISTICS OF AIRBORNE RADIOACTIVE MATERIAL Since the chemical and physical parameters of base surge are indirectly associated with the principal objectives of this project, only a brief summary of the Hardtack results is given here. The two subjects covered in detail are (1) fractionation and (2) base surge collection aboard the DD-592. Fractionation of radionuclides deposited on coracle surfaces becomes important when determining the maximum possible contribution to the free-field dose from such sources. The special collections aboard the DD-592 give some indication of the amount of water accompanying deposition at distances of approximately 3,000 feet from surface zero. This region is beyond the maximum throwout radius for both shots and yet stil] appears to be within a zone of heavy water deposition (Section 3.3.1). This water probably contains significant amounts of either dissolved or entrained fission products, but, according to the GITR records at these locations, most of this radioactive material was rapidly washed from coracie and ship surfaces. Deposition from the base surge at greater distances is very light and does not appear to be accompa- nied by such large amounts of water. — More detailed reports of the results obtained from the Hardtack samples may be found in the following reports: radiochemical analysis and fractionation (References 105 and 106); 318